The present invention relates to a substrate processing system for processing a substrate such as a semiconductor wafer in accordance with a photo-lithographic process.
In a manufacturing process of a semiconductor device, a semiconductor wafer is coated with a resist, and then the resist coating film is baked, exposed to light, and developed. Such a manufacturing process is carried out by using a substrate processing system (coating/developing system) disclosed in U.S. Pat. No. 5,664,254. In this system, resist coating, baking, and developing treatments excluding a light-exposure treatment are applied to a wafer. The process units are vertically stacked in multiple stages. A wafer is transferred to each of the process units by a main transfer arm mechanism which moves up and down along a transfer space arranged at the center of the system.
In the near future, the diameters of the wafers are planned to be changed from 8-inches to 12-inches (300 mm). When a large-size wafer is processed in accordance with a conventional system, the apparatus having quite a large footprint is required. In addition, the transfer arm must be moved horizontally for a long distance to transfer the large-size wafer, in other words, the moving stroke of the transfer arm becomes excessively long. As a result, the main transfer arm mechanism itself is enlarged more than required. Furthermore, the conventional system has a problem of a low maintainability since a maintenance operation must be applied from the outside the system.